The present invention relates to a composite flexible joint of the type having more particularly an inner core formed by a helical spring with contiguous turns, closed onto itself, with a circular cross-section and partly surrounding said spring, whereby at least one metal envelope which can be brought into contact with the parallel walls or surfaces effects sealing on either side of the spring by limited compression of the joint.
In a special embodiment of such an annular joint as described and claimed in French Pat. No. 2 151 186 in the name of the Commissariat a l'Energie Atomique the composite joint has two envelopes, the first made from a slightly ductile metal surrounding the spring of the inner core embedded in said envelope, whilst the second which is made from ductile metal partly surrounds the first envelope. These two envelopes have a C-shaped cross-section, whereby the joint can have a random contour, particularly shaped like a torus or having rectilinear sides joined by curvilinear portions. Preferably the spring constituting the inner core of the joint is made from steel, the first envelope from mild steel and the second envelope from aluminium.
According to various improvements to the above annular joints, particularly described and claimed in French Additions 2 224 029 and 2 232 235 to the above Main Patent the second envelope made from ductile metal may have its outer surface coated with a coating of a material with a low friction coefficient, such as polytetrafluoroethylene (Teflon), the inner spring also being associated with a rigid metal locking ring which limits the crushing of the spring. The continuous or discontinuous locking ring is positioned externally or internally of the spring.